Steeda S550 Mustang GT Differential Bushing Insert System - Street to Full Race Combo Kit (2015-2021)

15 Review(s)
$10.00 (4%)
Steeda Autosports has once again taken the S550 Mustang to the next level of performance and comfort with our exclusive S550 Mustang Differential Bushing Insert System - Street to Full Race Combo Kit GT!

Part Number: 555 4442
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Steeda Autosports has once again taken the S550 Mustang to the next level of performance and comfort with our exclusive S550 Mustang Differential Bushing Insert System - Street to Full Race Combo Kit GT! This combo kit comes complete with our Urethane and Aluminum Differential Bushing Insert Systems. When our engineers sat down to design these kits, we had to come up with a way to increase performance without sacrificing an ounce of drivability using urethane bushings. Our engineers then also took our hardcore racers into mind when designing our kit which utilizes aluminum bushings.

Unlike our competitors' kits that will absolutely increase NVH (noise, vibration, harshness), take 3-4 hours to install and force you to permanently modify the rear IRS suspension with a sawzall, Steeda's does not! Our kit installs in under 1 hour, adds little to no increase in NVH , is adjustable and can be easily removed - it simply doesn't get any better than this!

Both our urethane and aluminum bushing inserts aim to minimize pinion angle changes, increase traction, eliminate wheel hop and differential deflection.

Our urethane bushing inserts are made to Steeda's exact specifications and durometers, our kit comes with 3 different bushing options - our red 'street' 80 durometer bushings, our black 'performance' 90 durometer bushings, and our in-house billet 6061 aluminum bushings 'race'. Both urethane bushing options will increase performance with no increase in NVH, a Steeda-exclusive. Steeda's race kit installs in under 1 hour, is adjustable and can be easily removed. Since NVH was not an issue when designing the aluminum inserts, our engineers aimed to maximize reduction in wheel hop and differential deflection.

Steeda's kit adds the strength and support the OEM bushings need to perform the way our customers intended. Once again, this is not a permanent modification - there is no drilling, cutting or pressing required. Simply loosen and remove a couple bolts and this kit installs in less than 1 hour. Bushings are included for both the front and rear differential mounting locations. Grade 10.9 hardware is included with zinc-plated washers.

Note: Does not fit GT350 or Mach 1. Due to changes in the OE subframe bushings, the bushing inserts will not fit 2021 GT500's or 2022 Mustang's.

Product Benefits
  • Limits IRS differential movement while increasing traction and eliminating wheel hop
  • Urethane bushing inserts - little to no increase in NVH unlike the competition
  • Aluminum bushing inserts - designed for the abuse seen racing down the 1/4 mile
  • Easily removable, not a permanent modification
  • 100% designed, manufactured and made in the USA
  • Installs in 1 hour or less

CA Residents: Cancer and Reproductive Harm WARNING

Fitment & Features


Manufacturer: Steeda Autosports
Made in USA: Yes

Installation Information:

Level of Difficulty: Easy
Install Time: About 2 Hours
Tools Required: Basic Shop Tools

Vehicle Fitment:

Fits Model Year: 2015, 2016, 2017, 2018, 2019, 2020, 2021

Customer Reviews

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Average Customer Ratings


diff bushings inserts
so i am not sure what everyone was talking about in regards to being able to launch the car. i never got wheel hop from standing on it from a stop. i mean it's got more than enough to break them loose anytime from a start but mines been awesome and controlled from new. but will see if i can tell a difference after i get to drive the car when all the parts get installed.
Did you find this helpful?  1 of 9 Found Helpful
time to give props to Steeda
My car would not hook up at all. Basically if you gunned it in 1-3 you were burning rubber. The two kits I ordered were Stop the Hop and Differential Bushing Insert System. I opted for the metal bushing. I was worried about too much noise but it seems fine to me. Basically if you have loud exhaust I do know if you can even tell the difference. If anything the car sounds more connected to the transmission if that makes sense. It hooks up at least 70% better now and that's conservative. For those that are wondering about alignment, I had the car aligned at it's zeroed out perfect. Anyway it will still burn tires but it is night and day trying to manage. With this I do not have the feeling the car is going to do a 180 at any given time.
Did you find this helpful?  4 of 4 Found Helpful
First time the car hooked up for me without bouncing everyhwere
Steeda diff bushings were the biggest surprise. I have the subframe mounts on back order, so I will get them in next week. But I was amazed at the difference the bushings made. Only a slight wheel hop on wet roads. First time the car hooked up for me without bouncing everywhere. Used the red bushings, no noticeable NVH especially with the new exhaust. Can't wait to see how it does with the subframe mounts.
Did you find this helpful?  4 of 4 Found Helpful
The difference is night and day
Hey guys I just recently installed the the Steeda IRS & Differential bushings (red bushings) along with the IRS alignment kit. All I have to say is WOW! I installed it myself in the garage. It was very straightforward and easy. The difference is night and day. The car would have some really bad exaggerated wheel hop. I didn't feel much confidence with the car on launch and handling. I almost started to question my driving skills. On handling you get a lot of the control back. The car becomes more predictable when the rear breaks loose. When launching, it dips and rips off the line with very minimal wheel hop to where the car can grip. It's a very very good confident feeling you get. The wheel hop I would say is about 95% gone. The 5% wheel hop that you do feel is very light and almost unnoticeable. Anyone who is in doubt or questioning on getting the kit, I highly recommend it and it's worth every single penny. You won't regret it!
Did you find this helpful?  5 of 5 Found Helpful
This is the way the car should be with the PP
Since I was going to have the car up on jack stands in my driveway, I figured I'd do just about everything at once. Installed the Steeda IRS subframe bushing supports, alignment inserts, differential bushing supports(black), transmission bushing insert, and the Steeda shifter base bushing bracket along with the FR touring cat back. I had to have the upgraded bushing in the knuckle done at the Ford dealer. The bounce is gone! This is the way the car should be with the PP.
Did you find this helpful?  1 of 1 Found Helpful
The car feels so much more planted to the road
This is the first time I've ever done anything suspension wise to my car, David @ Steeda helped out greatly with all my questions as well as getting me setup with an install at their Pompano location with a tour of some badass shop cars and their facility. Everyone @ Steeda - David, Patrick, Matt were great and made sure I was happy with everything. I can't recommend their shop enough to anyone in the area and Matt did an awesome job with everything on the install, even tack welded my Gibson exhaust and turned their clamps a bit to help out. I won't have a chance to do pics this weekend of my spot on the beach as that will give a good before/after comparison when I put them together. The car feels so much more planted to the road, even just turning out of their parking lot I could tell everything felt more connected and precise to what I was telling the car to do. It basically now goes where I want it instead of reacting to what I'm asking it to do if that makes any sense at all? I had some open highway and did a little bit of careful back and forth in my lane and I felt completely planted and not bouncing around back and forth in my seat. Almost found myself doing slalom in between some construction barrels but given how my morning went I decided against it. The springs give the car the look I wanted and make the Vossen wheels look that much better. Nice tighter rebound than stock PP springs and reduces the overall bouncy ness on some of those highway stretches where it feels like you're hitting hydraulics for a half a mile. Also any bridges or overpasses with rough spots where you enter/leave them were solid. The MT-82 bushing insert is noticeable and I had much easier downshifts for highway passes on the way home, feels like a much more solid shift that I had to get a bit used to in a good way. I didn't do any hard launches or try to break the rear end loose at all since I was just getting used to it, will report back later on that. I can't really report on some of the individual IRS components since they all went in at the same time, but I am noticing a slight (and I mean slight) gear wine from the rear with the Black bushings. It's only really noticeable if you try to make it happen and barely push the gas at cruising speed. Nothing I'm worried about and after 4 hours of driving it home windows down and up for a few sprinkles it does not bother at me all. It's not all the time either or in any specific gear so no biggie as far as I'm concerned.
Did you find this helpful?  2 of 2 Found Helpful
I am pleased to say the thud is gone
So I was unaware that people had seen an improvement in the thud after installing the diff bushing so I hadn't really paid attention to it at all. My car is a GT PP with a ver obvious and annoying thud. Well, after paying more attention to it today I am pleased to say the thud is gone. That being said, I did notice a more pronounced shift if that is possible. Maybe a little more notchy, but I like it. Feels like the shifter drops into place easier. Bushings look to be a great investment and mod!
Did you find this helpful?  2 of 2 Found Helpful
I am beyond happy!
Got my Steeda differential bushing kit installed today...and I am beyond happy! I decided to go with the red Street bushings because I was afraid of NVH and I'd say the thud is 95% gone. It is at a point that I feel like if the car had come this way from the factory, I'd have never even noticed it. Such a joy to drive now and not hear that damn noise! I really think each car must do it to a different degree and mine was particularly bad because I just can't imagine anyone accepting that sound in a car otherwise so nice. I'm sure that with that kit or the Steeda aluminum bushings the sound would be 100% eliminated but I'm completely happy with it now and with the red Steeda's there is ZERO added NVH. Don't believe those that say you'll have to live with that awful sound. You don't. Haven't tested out the wheel hop but if that's better then that's just icing on the cake!
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Car lays down a solid pair of black lines off the line
Got mine, installed them, test drove the car. Wheel hop is about 90% gone now, with these, the bushing shims, springs, sways, BMR vertical links. All had an incremental improvement, adding up to good enough for me. Test drive I hear no more noise than before, no more vibration. Car lays down a solid pair of black lines off the line, with wheel hop gaps only showing in the top of the second gear black marks.
Did you find this helpful?  1 of 1 Found Helpful
I am a Steeda believer
The car is a totally different handling car. Took the wife for a ride today and she said it is smoother than before. Much less bouncy. That is good news to me. Cause if the wife is happy I am happy. But I will say that these mods have really changed my confidence in the car. I had one little 30mile spirited section with S curves on my way home that normally when they say 45mph.. you can take them at 55mph... I took them at 70mph and the car was just planted solid. No roll, no rebound and no breaking loose on the rear when I accelerated from the apex. It just transitioned smoothly and predictably. Now the only thing the wife did notice was the gear whine. Yes the Red differential bushing will cause some gear whine, but I have been told that replacing the stock gear oil in the rear end will help quiet that noise down. We will see as I will most likely change mine out here in the next week. Amsoil or Royal Purple is what a lot of people recommended. So, all in all, if someone is on the fence about these suspension upgrades, just do it. The guys at Steeda are top notch and know their stuff. Almost all of them have Mustangs and the owner even races them. A final shout out to [email protected] What a great help he was. He made sure everything was ready and there, his recommendations were spot on. David, again, Thank you man. I can hardly wait for the next batch of Steeda goodies come out.. Count me in already. I am a Steeda believer.
Did you find this helpful?  1 of 1 Found Helpful
Most noticeable improvement in the car
IRS differential bushings, aluminum: Most noticeable improvement in the car. Probably the best suspension mod I have made. Yes, you shift hard you'll feel a slight clunk as power hits to the rear end and has nowhere to go but to the tires, but that's exactly what I want. Car barely squats at this point and yet is still very comfortable for easy cruising. I have noticed a bit of driveline whine since installing them, but it's so light I don't even notice. Besides, I have a Corsa to listen to and that definitely drowns it out.
Did you find this helpful?  2 of 2 Found Helpful
Definitely worth purchasing
I installed the red bushings Friday night while installing my Borla S Type cat back. The red have no added HVH. Great street setup. Immediately on first take off noticed the rear axle was more solid. Definitely worth purchasing.
Did you find this helpful? 
wheel hop on my car is 100% eliminated
A couple of months ago, I started looking into overhauling the suspension of my 2015 GT PP. Up to that point, I had put about 7000 miles on my Mustang which allowed me to get a good sense of the issues with the IRS and overall suspension in stock form. Specifically, I wanted to stiffen up the entire rear end and eliminate the dreaded wheel hop while keeping NVH as close to the stock levels as possible. I also decided to replace the stock PP springs and sway bars in order to improve the overall handing, reduce body roll/brake dive and get rid of the bouncy ride. After going through a ton of feedback on the various solutions from the aftermarket (a lot of which came from fellow mustang6g members), I decided to go with Steeda. Below are the parts I chose to go with. Differential Bushings (Red/Street) Subframe Alignment Kit Subframe Bushing Support Vertical Links Rear Toe Link Subframe Suport Braces Linear Sport Springs Front and Rear Sway Bars and Billet Sway Bar Mounts Bumpsteer Kit I already had the Extreme G-Trak Brace installed. Now to the most important part...the results. The handling of the car is on a whole different level after the suspension upgrades. Minimal pitch and roll during braking, turns and transitions. Overall, the entire car is very tight with much better turn in. As expected, the biggest improvement is the rear end. The power delivery through the IRS is fantastic. The wheel hop on my car is 100% eliminated. The rear tires feel as if they are glued to the ground. Coming out of corners, I am able to get on the throttle earlier and more aggressively without any drama. In terms of NVH, I hear some gear whine in 6th gear under minimal throttle between 75 and 80mph (windows closed/stereo off) as a result of the differential bushing inserts. Apart from that, I can't tell a difference compared to stock. Even the ride quality feels great. My fiance couldn't tell that anything had been done to the car. Overall, I am very happy with the results. Props to Steeda for the excellent work they have done. In the near future, I am looking forward to adding a quality set of performance shocks/struts and hitting the road course.
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Solid Mod
Give yourself 3 hours to do this mod. No real increase in NVH Manual drive line slop is reduced further with these. SOLID MOD buy these. Not sure I would ever need the Aluminum ones but I bet I could swap them in an hour now that I'm familiar.
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No more chirp chirp chirp!
No more chirp chirp chirp! Went for a nice ride to check it out. I did a burnout and a hard take-off and it was very solid, no hopping. The most important thing was cornering for me. I went into a large parking lot, took a hard turn accelerating out of the exit purposefully braking the backend loose. Before, with the wheel hop, it was hard to control. It took a lot of working the wheel. Now it is easy! Thanks again [email protected] for the recommendation!
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